In general, examples of compounds used in manufacturing an LED, which determine a color of the LED include gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), gallium phosphide (GaP), gallium nitride (GaN), and the like.
Indiumgalliumnitride (InGaN) with a short wavelength is used for manufacturing a blue or green LED. Meanwhile, in the technology for manufacturing a white LED, the term “InGaN” is an acronym derived from several element materials such as indium, gallium and nitrogen.
Then, aluminungailiumarsenide (AlInGaP) with a long wavelength is applied to a red, orange, or yellow spectrum. This technology, called AlInGaP, uses aluminum, indium, gallium, and phosphorous (phosphide).
In general, in AlInGaP (aluminum indiumgallium phosphide), the percentages of Al and In are varied according to various known factors such as a required band gap and lattice matching with a galliumarsenide (GaAs) growth substrate.
Galliumarsenide (GaAs) absorbs visible light. Usually, when a growing process is ended, a gallium-arsenide (GaAs) substrate is removed, and is substituted with a transparent gallium phosphide (0% of Al and In) substrate.
A GaP-based material has a relatively high refractive index (about 3.5).
In such a condition, according to Snell's Law, a ray is reflected inward within an LED when not colliding against the wall surface of the LED within about 17° (critical angle) with respect to a normal line.
There is a problem in that since an LED chip is, in actuality, linear, the reflected light is repeatedly reflected with its incident angle even after several times of reflections, thereby weakening the light of the inside.
Also, in general, multiple LED chips are modularized, and used for various fields as well as lighting. However, this technology requires a complicated operation, process, and has a problem of heat generation per surface area due to an LED characteristic. In other words, due to a structure where the multiple LED chips are concentrated at one spot, high heat generation may be caused, thereby shortening a LED life span.